Germline Genetic Testing in Breast and Gynecologic Cancers: Evaluating Age at Diagnosis as a Determinant

Background: Breast cancer and gynecological malignancies, including cervical, ovarian, and endometrial cancers, remain leading causes of cancer incidence and mortality among women worldwide. This study investigated hereditary predisposition rates in women diagnosed with breast or gynecological cancer, focusing on the effect of age on germline pathogenic/likely pathogenic (P/LP) variant detection. We sought to determine whether younger age at diagnosis should be used as a criterion for patient selection for genetic testing. Methods: A total of 9084 consecutive females with breast cancer or gynecological tumors underwent germline NGS-based genetic testing (52 cancer-relevant genes) at Genekor laboratory from 2020–2026. Multivariable logistic regression evaluated factors associated with P/LP variant detection, adjusting for tumor type and family history. Results: Overall P/LP prevalence was approximately 20% (one in five patients), with tumor-specific rates of 19.24% in breast cancer, 27.59% in ovarian cancer, and 26.67% in endometrial cancer. P/LP prevalence declined significantly with age from 24.37% in patients <40 years to 15.90% in those ≥70 years, while Variants of Uncertain Significance (VUS) remained stable (40–43%). P/LP patients had earlier diagnosis (median 45 vs. 46 years, p < 0.001), driven predominantly by high-risk genes (13.87% in <40 y vs. 7.11% in ≥70 y). BRCA1 showed stronger age enrichment than BRCA2 (8.14% vs. 3.16% in <40 y; median diagnosis 43 vs. 45 years). Age remained independently associated with P/LP detection in multivariable analysis, with an 18% reduction in odds per 10-year increase for any P/LP (OR 0.82, 95% CI 0.78–0.86) and a stronger 28% reduction for high-risk variants (OR 0.72, 95% CI 0.67–0.78). Family history also independently predicted P/LP detection (OR 1.40, 95% CI 1.19–1.66). Conclusions: Although derived from a referral-based (and thus selected) population, these findings show that while younger patients have a higher prevalence of high-risk P/LP variants, clinically actionable findings are present across all age groups, including those ≥70 years. These results suggest that reliance on age alone to determine eligibility for genetic testing may be insufficient. Broadening access to testing beyond strict age-based criteria could improve the identification of hereditary cancer risk and inform patient management, although further evaluation in less selected populations is warranted.